Abstract: In an orthogonal frequency division multiplex communication system, for example a HIPERLAN/2 system, power amplifiers (224) of mobile terminals (4, 6) are switched off when not in use, and then switched on again when a signal transmission is to be made. This conserves power, but introduces a power amplifier transient (315). An access point (2), i.e. a type of base station, compensates for these power amplifier transients (315) using a simple scalar constant gain transient correction, over a full OFDM symbol (or a plurality of OFDM symbols). The correction is updated on an OFDM symbol by symbol basis (or plurality of symbols by plurality of symbols basis).

Abstract: A method of communication using Orthogonal Frequency Division Multiplexing (“OFDM”) comprises generating bit streams (bn?(0,1),n=0,1, . . . ,K?1) and the corresponding sets of frequency domain carrier amplitudes (XO(k) to XN(k)), where k is the OFDM symbol number, modulated as OFDM symbols to be transmitted from a transmitter. Prefixes are inserted as guard intervals in the sample streams and the OFDM symbols are transmitted from the transmitter to a receiver. The receiver uses information from the prefixes to estimate the Channel Impulse Response (H(F)D) of the transmission channels and uses the estimated Channel Impulse Response (?(F)D) to demodulate the bit streams in the signals received. The prefixes (?k.co to ?k.cD?1) are deterministic and are known to the receiver as well as to the transmitter. Preferably, the prefixes (?k.co to ?k.cD?1) comprise a vector (PD) that is common to said symbols multiplied by at least one weighting factor (?k).

Abstract: A method of channel estimation in a wireless orthogonal frequency division multiplexed (OFDM) communication system is disclosed. The method comprises receiving a signal in the time domain and applying a Fourier transform to the received signal to obtain a frequency domain signal including a plurality of sub-carriers. Then, the method requires estimating probabilities of coded bits for the plurality of frequency domain sub-carriers and performing channel coefficient estimation for the plurality of frequency domain sub-carriers using channel coefficient estimates for another of the plurality of frequency domain sub-carriers.

Abstract: A wireless communication unit (4160) comprises a processor (508) having a power-aware link adaptation function (540) for selecting an operational mode of the wireless communication unit (460) to transmit at least one data packet, the wireless communication unit (460) characterised in that the processor (508) is configured to perform, or is operably coupled to, a communication medium monitoring function that monitors an occupancy of a communication medium that comprises a plurality of communication links and, in response to a determination of i-he occupancy of the communication medium, the processor (508) performs link adaptation for at least one data packet transmission of the wireless communication unit (460). In this manner, in the provision of a power-aware link adaptation concept together with a communication medium occupancy monitoring function one or more of several links sharing the same communication medium can be selected to minimise power consumption within the wireless communication unit.

Abstract: A method of communication using Orthogonal Frequency Division Multiplexing (“OFDM”) comprises generating bit streams (bn?(0,1),n=0,1, . . . ,K?1) and the corresponding sets of frequency domain carrier amplitudes (XO(k) to XN(k)), where k is the OFDM symbol number, modulated as OFDM symbols to be transmitted from a transmitter. Prefixes are inserted as guard intervals in the sample streams and the OFDM symbols are transmitted from the transmitter to a receiver. The receiver uses information from the prefixes to estimate the Channel Impulse Response (H(F)D) of the transmission channels and uses the estimated Channel Impulse Response (?(F)D) to demodulate the bit streams in the signals received. The prefixes (?k.co to ?k.cD?1) are deterministic and are known to the receiver as well as to the transmitter. Preferably, the prefixes (?k.co to ?k.cD?1) comprise a vector (PD) that is common to said symbols multiplied by at least one weighting factor (?k).

Abstract: A system (100), receiver (160-190) and method of operation for spread OFDM wireless communication (single user OFDM-CDMA with cyclic-prefix) by: equalizing the received spread OFDM signal (y) and splitting it into first and second portions (?1, ?2); making a decision on the second portion and subtracting the second portion from the received signal to produce a first difference signal; processing the first difference signal to recover the first portion of the received signal in which symbol interfering terms of the second portion are substantially reduced; making a decision on the first portion and subtracting the first portion from the received signal to produce a second difference signal; and processing the second difference signal to recover the second portion of the received signal in which symbol interfering terms of the first portion are substantially reduced. The process may be iterated extensively at this stage.

Abstract: In an orthogonal frequency division multiplex communication system, for example a HIPERLAN/2 system, power amplifiers (224) of mobile terminals (4, 6) are switched off when not in use, and then switched on again when a signal transmission is to be made. This conserves power, but introduces a power amplifier transient (315). An access point (2), i.e. a type of base station, compensates for these power amplifier transients (315) using a simple scalar constant gain transient correction, over a full OFDM symbol (or a plurality of OFDM symbols). The correction is updated on an OFDM symbol by symbol basis (or plurality of symbols by plurality of symbols basis).

Abstract: Apparatus for estimating carrier and clock frequency offsets in OFDM systems employs a maximun likelihood estimator operation on the demodulated signals. The invention has the benefit of low complexity and obviates the need for any requirement for a dedicated training channel.